Unique Ring for Doorphone WT125 on TDA50

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We have installed many large home with doorphones on the TDA50 and NS700 due to the great wireless phones. One big problem is we install 7 wireless phones WT125 or TCA285 for example and they only need 2 cell stations to cover the entire home. When someone presses the door the customer wants all wired and wireless phones to use the ding-dong (20) ring sound however the wireless handsets cannot use the special doorphone ring pattern as they are in the PS ring group due to only 4 cell channels. Instead the wireless handsets use the Ring Group ring sound program which is no good. This causes both doorphone and co calls to have to use the same ring sound. How do I force the wireless handset to use the doorphone ring sound when in a PS ring Group? This is bad design by Panasonic and must have a way to fix. We cannot set the wireless handsets directly in ICD Group because of only 4 channels but 7 handsets. We have many customers with this problem.